Layer-dependent Schottky contact at van der Waals interfaces: V-doped WSe2 on graphene

Stolz, Samuel; Kozhakhmetov, Azimkhan; Dong, C.; Gröning, Oliver; Robinson, Joshua A.; Schuler, Bruno

doi:10.1038/s41699-022-00342-4

Cited by 15 publications

(18 citation statements)

References 47 publications

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“…It is worth noting that in a recent STM study performed on the same material system no subsurface vanadium dopants were observed. The clear visibility of buried impurities in cAFM is consistent with our model where tunneling is assumed to occur primarily between the tip and graphite substrate with impurities acting only as a local perturbation to the tunnel barrier.…”

Section: Resultsmentioning

confidence: 83%

Single Atomic Defect Conductivity for Selective Dilute Impurity Imaging in 2D Semiconductors

Loh

Chen

et al. 2023

ACS Nano

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Precisely controlled impurity doping is of fundamental significance in modern semiconductor technologies. Desired physical properties are often achieved at impurity concentrations well below parts per million level. For emergent two-dimensional semiconductors, development of reliable doping strategies is hindered by the inherent difficulty in identifying and quantifying impurities in such a dilute limit where the absolute number of atoms to be detected is insufficient for common analytical techniques. Here we report rapid high-contrast imaging of dilute single atomic impurities by using conductive atomic force microscopy. We show that the local conductivity is enhanced by more than 100-fold by a single impurity atom due to resonance-assisted tunneling. Unlike the closely related scanning tunneling microscopy, the local conductivity sensitively depends on the impurity energy level, allowing minority defects to be selectively imaged. We further demonstrate subsurface impurity detection with single monolayer depth resolution in multilayer materials.

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Section: Resultsmentioning

confidence: 83%

Single Atomic Defect Conductivity for Selective Dilute Impurity Imaging in 2D Semiconductors

Loh

Chen

et al. 2023

ACS Nano

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“…21,63−66 Very recently, Stolz et al have reported that vanadium is a p-type dopant for WSe 2 synthesized by metalorganic chemical vapor deposition. 67 It has been highlighted that the E F pinning and Schottky contact behavior show up upon the number of WSe 2 layers exceeding 2 due to the change of the band structure. 67 This affirms that the impurity dopant is one of the origins of E F pinning at the metal/TMD interface.…”

Section: Resultsmentioning

confidence: 99%

“…67 It has been highlighted that the E F pinning and Schottky contact behavior show up upon the number of WSe 2 layers exceeding 2 due to the change of the band structure. 67 This affirms that the impurity dopant is one of the origins of E F pinning at the metal/TMD interface. The E F of Ni/WSe 2 is pinned at 4.92 eV which is close to the valence band edge of the WSe 2 bulk crystal (5.33 eV).…”

Section: Resultsmentioning

confidence: 99%

Origins of Fermi Level Pinning for Ni and Ag Metal Contacts on Tungsten Dichalcogenides

Wang,

Hu,

Kim

et al. 2023

ACS Nano

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Tungsten transition metal dichalcogenides (W-TMDs) are intriguing due to their properties and potential for application in next-generation electronic devices. However, strong Fermi level (EF) pinning manifests at the metal/W-TMD interfaces, which could tremendously restrain the carrier injection into the channel. In this work, we illustrate the origins of EF pinning for Ni and Ag contacts on W-TMDs by considering interface chemistry, band alignment, impurities, and imperfections of W-TMDs, contact metal adsorption mechanism, and the resultant electronic structure. We conclude that the origins of EF pinning at a covalent contact metal/W-TMD interface, such as Ni/W-TMDs, can be attributed to defects, impurities, and interface reaction products. In contrast, for a van der Waals contact metal/TMD system such as Ag/W-TMDs, the primary factor responsible for EF pinning is the electronic modification of the TMDs resulting from the defects and impurities with the minor impact of metal-induced gap states. The potential strategies for carefully engineering the metal deposition approach are also discussed. This work unveils the origins of EF pinning at metal/TMD interfaces experimentally and theoretically and provides guidance on further enhancing and improving the device performance.

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“…However, the same work reports a (Mo:Re)S 2 ML alloy, whose metastability window is small and high in energy (see Figure a and SI Figure S2). Another recent report characterizes (V:Mo)S 2 MLs experimentally, which is also a TM pair likely to mix according to our analysis. The first example mentioned above, (Mo:W)S 2 (green lines in Figure a), has also been realized in experiments. , Finally, V-doped WSe 2 and (Mo:W)Se 2 alloys have been recently synthesized − as non-MoS 2 -based examples that are both indicated as likely miscible alloys in Figure b.…”

Section: Optimal Prototypes For Alloysmentioning

confidence: 90%

“…The first example mentioned above, (Mo:W)S 2 (green lines in Figure 4 a), has also been realized in experiments. 16 , 39 Finally, V-doped WSe 2 and (Mo:W)Se 2 alloys have been recently synthesized 40 − 42 as non-MoS 2 -based examples that are both indicated as likely miscible alloys in Figure 4 b.…”

Section: Optimal Prototypes For Alloysmentioning

confidence: 99%

Design Guidelines for Two-Dimensional Transition Metal Dichalcogenide Alloys

et al. 2022

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Two-dimensional (2D) materials and transition metal dichalcogenides (TMD) in particular are at the forefront of nanotechnology. To tailor their properties for engineering applications, alloying strategiesused successfully for bulk metals in the last centuryneed to be extended to this novel class of materials. Here we present a systematic analysis of the phase behavior of substitutional 2D alloys in the TMD family on both the metal and the chalcogenide site. The phase behavior is quantified in terms of a metastability metric and benchmarked against systematic computational screening of configurational energy landscapes from First-Principles. The resulting Pettifor maps can be used to identify broad trends across chemical spaces and as starting point for setting up rational search strategies in phase space, thus allowing for targeted computational analysis of properties on likely thermodynamically stable compounds. The results presented here also constitute a useful guideline for synthesis of binary metal 2D TMDs alloys via a range of synthesis techniques.

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Layer-dependent Schottky contact at van der Waals interfaces: V-doped WSe2 on graphene

Cited by 15 publications

References 47 publications

Single Atomic Defect Conductivity for Selective Dilute Impurity Imaging in 2D Semiconductors

Single Atomic Defect Conductivity for Selective Dilute Impurity Imaging in 2D Semiconductors

Origins of Fermi Level Pinning for Ni and Ag Metal Contacts on Tungsten Dichalcogenides

Design Guidelines for Two-Dimensional Transition Metal Dichalcogenide Alloys

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